Ten healthy adult volunteers (5 males, 5 females; 20-62 years) were recruited and inhaled 163.3 ppm (SD: 4.0) NO for 30 min, 5 times daily, for 5 consecutive days. Lung function and blood levels of methemoglobin, nitrites/nitrates, prothrombin, pro-inflammatory cytokines and chemokines were determined before and during treatment.
All individuals tolerated the NO treatment courses well. No significant adverse events occurred and three minor adverse events, not attributable to NO, were reported. Forced expiratory volume in 1 sec%predicted and other lung function parameters, serum nitrites/nitrates, prothrombin, pro-inflammatory cytokine and chemokine levels did not differ between baseline and day 5, while methemoglobin increased significantly during the study period to a level of 0.9%(SD: 0.08) (p < 0.001).
These data suggest that inhalation of 160 ppm NO for 30 min, 5 times daily, for 5 consecutive days, is safe and well tolerated in healthy individuals.